Tumor suppressor activity of PTPRJ, a receptor type protein tyrosine phosphatase, in human melanoma cells

131PTPRJ expression is downregulated in a variety of cancer cells and human tumors. Loss of heterozygosity (LOH) was found in human mammary, colon, lung and thyroid specimens. Furthermore, Ptprj, the mouse homologue of PTPRJ, was proposed as a tumor susceptibility gene for colon cancer. Interestingly, PTPRJ had therapeutic effects in thyroid, mammary and pancreatic cancer cells.
 The aim of this study was to investigate the role of PTPRJ in human melanomagenesis. We measured by immunohistochemistry PTPRJ protein expression on a tissue array containing 200 human melanoma tissue specimens; PTPRJ staining is low or absent in the majority of tumor cells compared to normal melanocytes contained in the same sections. Reduced or absent expression of PTPRJ was also assessed by Western blot analysis in a panel of 12 cell lines compared to normal cultured melanocytes. Also, we …